The first study on CCs for a sample of FG candidates was done by [1]}. In their work, the authors studied four isolated elliptical galaxies selected from ROSAT X-ray data and confirmed as fossil systems with a dedicated optical follow up. It is worth noting that the authors suggested that these objects could be FGs, but at the time no operational definition was available, so no \(\Delta m_{12}\)  is computed in their paper. However, at least three out of four were later confirmed as FGs in other publications, confirming the accuracy of their approach. [1]} results indicated the presence of CCs in the central regions of these objects.
